The invention relates to a method for reconstructing the amplitude/phase diagram of a transmit/receive module of a phased-array antenna, in particular an active phased-array antenna.
In the future, active phased-array antenna radar systems will need a large number of transmit/receive modules at a low cost. The amplitude and phase of these modules can be adjusted (multi-state device). If, for example, a 6 bit phase shifter and a 6-bit amplitude positioner are entered, the result is 26xc3x9726=4,096 different amplitude/phase states of the transmit/receive module.
The total amplitude/phase response of a transmit/receive module is usually shown in a so-called amplitude/phase map. FIG. 1 shows an example of such an amplitude/phase diagram. The phase is plotted along the abscissa; the amplitude, along the ordinate. Each individual measurement point inside the two-dimensional amplitude/phase plane represents the measured amplitude and phase for a specific amplitude/phase state of the transmit/receive module.
To control the transmit/receive module in the active phased-array antenna, the total amplitude/phase response in both the receive and the transmit mode must be known in the specified frequency range for each transmit/receive module.
Since it is typical for modern radar systems to have a large number of transmit/receive modules (airborne radar typically has 1,000 transmit/receive modules) with 2nxc3x972n different amplitude/phase states respectively, it is no longer feasible to measure in total all of the amplitude/phase states of each transmit/receive module, first from the viewpoint of an enormously large volume of data and, second from the viewpoint of cost (extremely time consuming).
The article by Wilden, H.: xe2x80x9cMicrowave Tests on Prototype T/R Modules.xe2x80x9d IEE International Radar Conference, Edinburgh, pp. 517-521, 1997, discloses the details on the measuring range for testing the transmit/receive modules of a phased-array antenna.
According to DE 39 34 155 C2, the total energy emitted by the transmit/receive elements of a phase array antenna is measured by means of a receive antenna. The amplitude of each transmit/receive element is determined from the change in the total energy, while the phase of each phase shifter of the array antenna is changed.
In JP 2000119773A, to determine the amplitude/phase distribution of a phased-array antenna, the amplitude of a beam of rays is measured while the phase is varied. Then the total distribution is found with the aid of field conversion and repeated calculation until the solution converges.
According to JP 10132880A, to determine the phase distribution of a phased-array antenna, the phase of a transmit element is measured at a fixed frequency for each angle. Then the phase of an element is measured at a fixed angle for different frequencies. For the non-measured angles or frequencies, the phase is then calculated on the basis of the measurements.
The object of the invention is to develop a synthesis algorithm, which makes it possible to reduce the number of measurement points and to reconstruct the behavior of the total amplitude/phase response.
This problem is solved with the methods disclosed according to principles of the invention, wherein a method for reconstructing the amplitude/phase diagram of a transmit/receive module for a phased-array antenna, includes measurement of amplitude and phase of the amplitude/phase states (a, i), where i=imin . . . imax of an individual amplitude state a; and the measurement of amplitude and phase of the amplitude/phase states (j, b), where j=jmin . . . jmax of an individual phase state b. Reconstruction of the amplitude values of an amplitude state x is accomplished by shifting the measured amplitude values of the amplitude state a by the difference xcex94A of the measured amplitude values of both amplitude/phase states (x, b), (a, b), which within the phase state b belong simultaneously to the amplitude state x or the amplitude state a. There is also reconstruction of the phase values of a phase state y by shifting the measured phase values of the phase state b by the difference xcex94"PHgr" of the measured phase values of both amplitude/phase states (a, y), (a, b), which within the amplitude state a belong simultaneously to the phase state y or the phase state b.
With the inventive method, the time and subsequently the cost of characterizing (i.e., measurement data acquisition) the transmit/receive modules can be reduced to a fraction of what is currently needed.
Other objects, advantages, and novel features of the present invention will become apparent from the following detailed description of the invention when considered in conjunction with the accompanying drawings.